An example of a known technique for detecting the position of an object is a system that includes a position detecting antenna and a shelf-wireless tag which are disposed on each shelf being an object. The IDs of the wireless tags affixed to the shelves are registered for each shelf in advance in a shelf tag management table in a position management server. A position detecting section in the position management server determines the position of each shelf, using identifying information received from wireless tags affixed to other shelves by the position detecting antenna disposed on each shelf and data stored in the shelf tag management table.